A so-called Kinyon pump or a rotary-type air locker combined with a low- or medium-pressure Roots blower is well known as means for pumping a powdery or granular material. However such pumps are not widely utilized, because the Kinyon pump has the defect that it causes considerable damage to the powdery or granular material due to the sealing system thereof, and also that it requires a comparatively large amount of power. The rotary air locker system has the defects that the mixing ratio (weight ratio of air to pumped material) is small, the efficiency is low, air loss is inevitable due to the structure of the air locker, it is not possible to utilize the rotary-type air locker with all kinds of powdery or granular material, the expense of recovering the powdered material at the exit end due to the low mixing ratio thereof is high, it is useful only for comparatively short distances of transmission, etc. A batch system of pumping is also known, such as the Seller-type and Flaxo-type systems, both of which are operated by alternately connecting therewith a plurality of batch tanks for carrying out a continuous operation, so that economy of operation cannot be obtained except in a large scale plant.